Summary
This report supplements "Report on research into the mouthing behaviour of children up to 5
years old – Executive Summary" (DTI, 2002).
This report presents background information to the study and further data and discussion from
the study, specifically:
i) Information regarding the methodology and protocols of the study
ii) Background data on the sample: Details of children’s mouthing habits, the child’s family, the
observers and their care and work circumstances and child care arrangements
iii) Estimated data on time spent each day mouthing on dummy/soothers, fingers, toys, and other
objects by how the items were mouthed, for each age group
iv) Details of the validation study
v) Discussion of the findings of the work
vi) Details of the items mouthed in the study
vii) Literature review of chemical and mechanical hazards from children’s toys and other plastic items
viii) The forms used in data collection.
Information presented in this report should be used in conjunction with the summary report described above.
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Chapter 1
Design of the Research
1.1 AIMS OF THIS RESEARCH
The research described in this report was designed to expand upon the knowledge of the
mouthing behaviour of children. The ages of children to be observed in this study ranged from
1 month to 5 years, to investigate the extent of exposure to products at this older age (given the
findings of Warren et al. (2000) that over 20% of the children in their study carried a non-nutritive
sucking habit past the age of 36 months). The overall aim of the project was to produce a figure
for the total time that children within this age range are expected to mouth items per day. This
could then be used to assess potential mechanical hazards posed by items on which children
were found to mouth.
1.2 DATA COLLECTION
The behaviour of young children may be greatly affected by all types of stimuli. In studies such
as this where we are attempting to gain information on normal and natural behaviour of children
it is imperative that the environment in which the data are gathered is as unaffected by the
observation as possible. This means that the child should be surrounded by things that they are
used to and know. For this reason, the research by Groot et al (1998) and Juberg et al (2001) both
rely on data being recorded by the parent(s) of each child using a diary format. The child is
obviously used to the presence of their parent and so natural behaviour may be assumed. The
use of a structured formal diary recording system serves to control the type of information that
the parent is recording and therefore provides a level of validity and reliability to the research.
Greater levels of reliability would possibly be obtained through the use of trained researchers
observing the child in their home environment, as the observer is trained to record certain types
of behaviour consistently, and so providing good repeatability of observation. The same is true
for the use of video recording equipment, where very short behaviours can be reliably recorded.
However, it is likely that a child will be very aware of a video camera and being filmed, and this
could lead to a change in behaviour. Likewise, the presence of a stranger in the home is likely to
alter the behaviour of the child being observed to a greater or lesser extent, so while the
reliability of the data may be high, the circumstances are less "realistic" and lower the validity of
the data. Another problem with video recording is that young children are often on the move,
which would make capturing every behaviour extremely difficult. For these reasons this research
used parents/carers as observers, to ensure children’s mouthing behaviour, and behaviour
generally, were as natural as possible to ensure high data validity.
Observations were carried out at home rather than nurseries or childcare establishments as the
home environment has a vast range of items that are accessible to children, not all of which are
intended for use by them. This is a worst case scenario but also realistic compared to more sterile
environments such as playgroups and nurseries where the contents of rooms are very carefully
and rigidly controlled.
Because of the factors mentioned above it was felt that an examination of the reliability of
parents as observers should be carried out. This has not been investigated by prior studies
which have also used parents as observers. A comparison of parent and trained observer data
collection was carried out on a sample of 25 children. Information on this validation part of the
research may be found in Section 5 of this report.
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1.3 EXPERIMENTAL DESIGN
Observation was carried out by parents in the child’s home for a total of five hours, split into 20
fifteen minute observation sessions. A period of two weeks was allowed for the observations to
be completed and the data returned. These observation sessions were to be spread out over
different times of the day and the week as follows:
i) Weekdays:
• 4 fifteen minute sessions between the child waking and 11am
• 4 fifteen minute sessions between 11am and 2 pm
• 4 fifteen minute sessions between 2pm and 6pm
• 4 fifteen minute sessions between 6pm and the child going to bed for the night
ii) Weekend:
• 1 fifteen minute session between the child waking and 11am
• 1 fifteen minute session between 11am and 2 pm
• 1 fifteen minute session between 2pm and 6pm
• 1 fifteen minute session between 6pm and the child going to bed for the night.
This gives in total 5 hours of observation time on each child. Observations could be done at
the discretion of the parent at any time within these zones. However, no more than two
observation sessions were allowed within the same time zone on any one day, and at least 30
minutes was required to be left between observation sessions. These provisions were included
in order to ensure data was gathered spread evenly across the days and week to gather a
representative picture of the child’s behaviour, and also to reduce potential errors from fatigue
caused by observation.
In each 15 minute observation session the following information was recorded:
• the duration of each mouthing behaviour
• what types of items were mouthed
• the type of mouthing behaviour for each item mouthed
• what was mouthed
• which room of the house the observation was undertaken in
• other people present in the room
• whether the child was feeling unusually ill or tired during the observation
• how long it had been since the child last ate and slept
• what the child was doing during the observation.
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Information gathered over the whole study for each participant also included:
• details of the child’s physical and psychological development
• details of the child’s family (e.g. size, type of house lived in, social class)
• details of the time the child spent outside of the family home in a care environment
(e.g. a nursery, playgroup)
• details of toys mouthed by each child, part of toy mouthed and what each part mouthed
was made of
• details of what other objects were mouthed and what they were made of
• details of the child’s daily routine for the first and last days that they were observed i.e. what
time they got up and went to bed, and time spent eating and sleeping during the day.
The questionnaires and forms used to gather these data are presented in Appendices A, B, C and D.
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Chapter 2
Methodology
2.1 DEVELOPMENT OF MATERIALS
2.1.1 Pre-pilot trials
The use of a diary type observation recording system requires that the forms for recording
behaviour are simple and intuitive to complete. For this reason, a pre-pilot stage was undertaken.
Several alternative observation recording forms were produced and trialed in a local day nursery
by members of the Product Safety and Testing Group (PSTG) trained in observation protocols. For
the purposes of this stage, a single child was observed by both members of the PSTG for a
15 minute period, with the type and duration of each mouthing behaviour being recorded. This
process was repeated for each of the sample forms in turn. The results were then analysed for
the similarity of findings between the two members in terms of duration and type of behaviours.
Ease of use of each form was also assessed. One observation recording form was chosen to be
used in the pilot trials.
2.1.2 Pilot trials
The materials developed for use in the pilot trials were as follows:
• Consent form
• Set of written instructions
• Observation recording form (as trialed in the pre-pilot stage)
• Questionnaire
• Daily routine form
• Toy and object details forms.
Also included in the observation pack were a stop-watch, a pen and a freepost labelled
envelope for returning the completed observations.
The pilot trials followed the same format that was proposed for the main part of the study.
Participants were given the folder containing all the required materials (as listed above). They
were given only brief instructions about what they were being asked to do, as it was anticipated
that the only contact with participants taking part in the main study would be on the telephone,
and so the main instructions included in the observation pack would provide all of the necessary
information. Participants were given one week to complete the five hours observation time.
Seven parents were recruited to undertake the observations of their child for the purposes of
pilot testing the protocols and materials developed for the research. Two were unable to
complete the study for personal reasons, and results from one participant did not arrive back at
the PSTG until after the deadline for analysis, providing data from four participants for analysis.
The ages of the children observed were 4 months (female), 10 months (male), 27 months
(female) and 55 months (female). Feedback was obtained from each participant on the ease of
use of the materials contained within the observation pack which resulted in changes being
made to the documents. The final versions that were then used in the main study are presented
in Appendices A to D.
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2.2 OBSERVATION PROTOCOLS
2.2.1 Timing of mouthing behaviours
Participants in the research were each provided with a stopwatch for timing the duration of
mouthing events. They were not required to start, stop and reset the watch each time an event
occurred. Instead, the stopwatch was started at the beginning of the session and not stopped
until the 15 minutes was over. When the behaviour began, i.e. when the item first entered the
mouth, the time on the stopwatch was recorded on the observation form (to the nearest second),
and when that particular behaviour finished the time was again noted. This enabled a quicker
and more accurate time map of the child’s behaviour to be produced than by starting and
stopping the watch for each behaviour, especially for very short time behaviours.
2.2.2 Classifying what was mouthed
Products/items mouthed were classified into four categories: a dummy/soother, fingers,
toys, and other objects. The "fingers" category includes any part of the body of the child or of
another person, and whether an item was classified as a toy or other object was decided upon
by the observer.
2.2.3 Classifying the type of mouthing behaviour
Mouthing behaviour was classified into three categories. The instructions given to observers on
how to classify behaviour were as follows:
• Licking/lip touching. This is where the item is placed to the front of the mouth, without
actually entering into the mouth. The child may be actually licking an object, or may be
touching the object to their lips. The time recorded should be from when the object first
touches the child’s mouth to when the object is no longer in contact with the mouth. If a
child is licking an object it may be difficult to record because of the short time period
involved. In this case note the time when the object is put close to the mouth to be licked,
and then taken away from the mouth
• Sucking/trying to bite. The item is put directly into the mouth of the child. The child may
be sucking, holding the object in their mouth or trying to bite (gumming) the object
• Biting or chewing. The item is directly in the mouth of the child. It is clear that the child is
biting or chewing on it.
It can be difficult to tell exactly what a young child is doing with an item if it is in or near their
mouth. Observers were told that unless they could see that actual biting or chewing was
happening they should tick the sucking/trying to bite category. If the child did more than one
action then they were asked to tick both, e.g. if they lick and then bite an item to put a tick under
both headings. Photographs were included illustrating the licking and sucking behaviours, as
shown in Appendix E, but not biting/chewing; this is difficult to illustrate as the item is shown as
just being at/inside the mouth without the movement which means chewing or biting is occurring.
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Chapter 3
Participant Details
236 children were observed by their parents. The number of children observed in each age
group were as follows:
Age group Number of boys Number of girls Total
1-3 months 3 6 9
3-6 months 7 7 14
6-9 months 6 9 15
9-12 months 6 11 17
12-15 months 5 11 16
15-18 months 5 9 14
18-21 months 11 5 16
21-24 months 6 6 12
2 years 18 21 39
3 years 13 18 31
4 years 17 12 29
5 years 14 10 24
Table 1: Number of children observed in each age group
The upper age limit for each age group was the day before the final month age is reached,
e.g. 1-3 months includes children from one month to two months three weeks and six days.
3.1 CHILDREN'S MOUTHING CHARACTERISTICS AND CHILDCARE DETAILS
Background information was gathered on each child and their families, covering the child’s
physical development, mouthing habits of the child, and information on the child’s family.
The information collected is detailed below.
i) The mouthing habits of the child:
• 29% of children leave bite marks in toys
• 25% of children damage items by biting
• 28% of children use a dummy/soother
• 69% of children were/are breast-fed
ii) Who did the observations, who cares for the child, do they work:
• 99% of the observations were done by the child’s mother
• 97% of the children were (mainly) cared for by their mother
• 47% of main carers did not undertake paid work, 50% worked part-time, 3% worked full-time
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iii) Childcare arrangements:
Childcare arrangements for each child observed ranged from none (i.e. always at home with the
mother or father) to 5 days a week. Details are presented in Figure 1 of the type of childcare that
children taking part in the study attended. For each day of childcare separate values are
presented, for example, day one is not necessarily the same day for all children but instead means
that this represents a single day (or part of a day) where childcare occurs for that child.
Day one
none
creche
playgroup
relative / friend
childminder
nursery
Day two
none
creche
playgroup
relative / friend
childminder
nursery
Day three
none
creche
playgroup
relative / friend
childminder
nursery
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Day four
none
creche
playgroup
relative / friend
childminder
nursery
Day five
none
creche
playgroup
relative / friend
childminder
nursery
Figure 1: Childcare arrangements, by day, for children observed in the study.
As the number of observation days increases the number of children going to some form of
childcare decreases. Nursery is the most popular form of childcare.
Information was gathered on how much time during a typical normal day the child would have
available to spend mouthing, that is, time not spent sleeping or eating.
Table 2 presents the mean, minimum and maximum times available to mouth for each age group
Age group Mean Minimum Maximum
1-3 months 8:22 3:51 13:30
3-6 months 9:09 6:20 12:48
6-9 months 9:21 7:10 11:50
9-12 months 9:06 6:45 11:23
12-15 months 9:15 7:20 11:05
15-18 months 9:50 6:57 12:42
18-21 months 10:10 8:30 12:15
21-24 months 10:12 6:50 13:39
2 years 10:45 7:35 13:20
3 years 11:10 9:35 13:50
4 years 11:31 9:40 14:10
5 years 11:22 9:30 14:00
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Chapter 4
Results
The following sections present results for:
4.1 Estimated mouthing time according to what was mouthed
4.2 Estimated mouthing time according to what was mouthed and how it was mouthed
4.3 A breakdown of what was mouthed, including by material (and if it is intended to be
mouthed – as far as can be known).
The estimated daily mouthing time is extrapolated from the mouthing behaviour recorded
over the five hours observation time. This is calculated as follows:
Observed mouthing time
* time available to mouth per day
Total time observed for
Where:
Observed mouthing time = the amount of mouthing time recorded for each child
Total time observed for = the total amount of time that they were observed for (5 hours)
Time available to mouth = the time available over the whole day for the child to mouth
per day i.e. the time during the day when they were awake but not eating
This calculates the average time spent mouthing per hour, multiplied by the total number
of hours each day that each child has available to mouth i.e. the number of hours they are
awake during the day but not eating. This has been based on the assumption that children are
likely to mouth at the same rate throughout the day. A Kruskal-Wallis1 test showed no
significant differences in observed mouthing between the different times of the day that
children were observed.
The presented mean values were calculated by dividing the total estimated mouthing time for
each category of item mouthed within each age group by the total number of subjects in that age
group. For example, for 3-6 months olds, only 4 subjects may have actually mouthed on a
dummy/soother but the total estimate of daily mouthing on a dummy/soother for that age was
divided by the total number of subjects in that age group (14) to give the mean value of daily
mouthing time that could be expected across that age group generally.
Because of the skewed2 nature of the raw data used to produce these estimates care should be
taken if using mean estimated daily mouthing values for the purposes of safety. This is because
the mean value may not reflect the true average or middle value of the sample for each age
group, depending on the degree to which the data are skewed.
4.1 ESTIMATED DAILY MOUTHING TIME BY ITEM MOUTHED
Figure 2 presents the mean estimated daily mouthing time for males and females combined for
each item mouthed (in hours:minutes:seconds). Each mean behaviour is the average time that a
child in each age group could be expected to mouth a given item over a normal day. Mean total
daily mouthing time is the time that any child could be expected to mouth, on anything, on
average over a normal day, and is the sum of mean mouthing time on all items for each age group.
1
The Kruskal-Wallis test is a non-parametric statistical test used to determine whether values of scores for three or more groups are significantly different, in
this case we have four groups, i.e. those observed between waking and 11am, between 11am and 2pm, between 2pm and 6pm, and 6pm until bedtime.
2
Page 12 The observed data have a skewed distribution because in general a high percentage of observed mouthing behaviours for each age group were very short in
nature (i.e. only a few seconds), with only a small percentage being observed with duration of between 1 and 15 minutes.

Table 3 presents the mean and maximum estimated daily mouthing data, for males and females
combined. Data shown for males and females combined as a Mann-Whitney1 test showed no
statistically significant difference in mouthing time between the sexes.
The presented maximum values are the highest estimated daily mouthing times of any child in
each age category, for each item. It does not necessarily follow that the maximum values in each
age group for each item were exhibited by the same child, that is, one child may have mouthed
a lot on a dummy/soother while another child in the same age group may have mouthed a lot on
fingers. Also presented is the maximum estimated daily mouthing time for mouthing on all and
any items, in each age group, by any single child.
2:15:00
2:00:00
1:45:00
Dummy / Soother
Mean mouthing time
1:30:00 Fingers
1:15:00 Toys
1:00:00 Other objects
0:45:00 Not recorded
Total
0:30:00
0:15:00
0:00:00
2
3
4
5
1-3
3-6
6-9
9-12
12-15
15-18
18-21
21-24
Age category
Figure 2: Estimated mean daily mouthing time for each item mouthed and for all items (total
mouthing) (hours:minutes:seconds)
1
The Mann-Whitney test is a non-parametric statistical test used to determine if there are significant differences between scores or values of two groups
with different subjects in each group, i.e. males and females.
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No clear age pattern exists for total mouthing time, with the highest estimated daily mean mouthing
time being exhibited by children aged 18-21 months. However, a Kruskal – Wallis test for
differences in observed mouthing time on all items between the age groups was significant (Chi-
square = 30.050, d.f. = 11, p

4.2.1 All items
Estimated daily mean mouthing time is presented in Figure 4, for mouthing on all items, by how
items were mouthed at each age group.
2:15:00
2:00:00
1:45:00 lick, suck and bite
suck and bite
Mean mouthing time
1:30:00
lick and bite
1:15:00
lick and suck
1:00:00
bite
0:45:00 suck
0:30:00 lick
0:15:00
0:00:00
1-3
3-6
6-9
9-12
12-15
15-18
18-21
21-24
2
3
4
5
Age category
Figure 4: Estimated mean daily mouthing on all items by how they were mouthed
(hours:minutes:seconds).
Sucking is shown to be the most common mouthing behaviour at all ages.
4.2.2 Dummy/Soother
Figure 5 shows how dummies/soothers were mouthed at each age group, and Table 5
presents the estimated daily mouthing data shown in Figure 5.
1:20:00
1:10:00
Not recorded
1:00:00
Lick, Suck and Bite
Mean mouthing time
0:50:00 Suck and Bite
Lick and Bite
0:40:00
Lick and Suck
0:30:00 Bite
Suck
0:20:00
Lick
0:10:00
0:00:00
1-3
3-6
6-9
2
3
4
5
9-12
12-15
15-18
18-21
21-24
Age category
Figure 5: Estimated mean daily mouthing time for dummy/soothers according to how they
were mouthed (hours:minutes:seconds).
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